Watershed Modeling Advanced DEM Delineation

Transcription

1 v WMS 10.1 Tutorial Watershed Modeling Advanced DEM Delineation Techniques Model manmade and natural drainage features Objectives Learn to manipulate the default watershed boundaries by assigning map features such as road embankments, gutters, and known watershed boundaries to watershed delineations. Prerequisite Tutorials Watershed Modeling DEM Delineation Required Components Data Drainage Map Time minutes Page 1 of 20 Aquaveo 2016

2 1 Introduction Getting Started Use Stream Arcs to Manipulate Basin Delineation Open DEM Data Open Background Topographic Map Image Run TOPAZ Basin Delineation Display Flow Directions Add Stream Arcs Along Railroad Basin Delineation with the New Stream Save the Project Depression Points Depression Attribute Run TOPAZ Create Outlet Point Create Stream Arc Basin Delineation for the Depression Point Compute Storage Capacity Curve Time of Concentration Arcs Polygon Basin IDs to DEM Smoothing Boundaries Conclusion Introduction Some terrain features including roads, canals, dams, dikes, or levees are not well represented in DEMs, especially if the DEM resolution is coarse. This can lead to erroneous automated watershed delineation. In addition, it may be desirable to evaluate future alterations in terrain that result from development scenarios. WMS has tools for manipulating DEM delineation results in order to accurately represent the actual watershed drainage basins. This exercise teaches how to manipulate DEM data for more accurate drainage analysis by discussing and demonstrating how to use stream arcs to manipulate basin delineation, how to handle depressions, how to develop time of concentration according to the longest flow path, how to map polygons representing drainage basins to the DEMs, and how to smooth results for reporting and presentations. 2 Getting Started Starting WMS new at the beginning of each tutorial is recommended. This resets the data, display options, and other WMS settings to their defaults. To do this: 1. If necessary, launch WMS. 2. If WMS is already running, press Ctrl-N or select File New to ensure that the program settings are restored to their default state. 3. A dialog may appear asking to save changes. Click No to clear all data. The graphics window of WMS should refresh to show an empty space. Page 2 of 20 Aquaveo 2016

3 3 Use Stream Arcs to Manipulate Basin Delineation Sometimes it is necessary to add stream arcs to a basin to represent water that accumulates along man-made objects such as roads. Roads often disrupt the natural flow of watersheds, acting as a barrier that collects water creating something similar to a stream. The water collected along a road needs to be "added" into the watershed in order to properly model the hydrology. Stream arcs can be used to edit flow directions associated with the DEM routing water into the proper drainage basins. 3.1 Open DEM Data 1. Click Open to bring up the Open dialog. 2. Select NED GRIDFLOAT header (*.hdr) from the Files of type drop-down. 3. Browse to the demedit\demedit\ \ directory and select hdr. 4. Click OK to exit the Open dialog and bring up the Importing NED GRIDFLOAT File dialog. 5. Click OK to close the Importing NED GRIDFLOAT File dialog. 6. Click Yes when prompted to change the projection and open the Reproject Object dialog. 7. In the Project projection section, turn on Set. 8. In the Horizontal section of the Project projection section, select Global Projection. 9. Click Set Projection to bring up the Select Projection dialog. 10. Select UTM from the Projection drop-down. 11. Select 11 (120 W 114 W Northern Hemisphere) from the Zone drop-down. 12. Select NAD83 from the Datum drop-down. 13. Select METERS from the Planar Units drop-down. 14. Click OK to close the Select Projection dialog. 15. In the Vertical section of the Project projection section, select Local from the Projection drop-down and Meters from the Units drop-down. These should match the same options in the Vertical section in the Object projection section. 16. Click OK to close the Reproject Object dialog. Now change the display options so make sure the project is visible. 17. Click Display Options to bring up the Display Options dialog. 18. Select DEM Data from the list on the left. 19. On the DEM tab, turn on Stream, Flow Accumulation, Color Fill Drainage Basins, Fill Basin Boundary Only, and DEM Contours. 20. Select Map Data from the list on the left. 21. On the Map tab, turn off Color Fill Polygons. Page 3 of 20 Aquaveo 2016

4 22. Click OK to close the Display Options dialog. The Graphics Window should appear similar to Figure 1. Figure 1 Initial project appearance 3.2 Open Background Topographic Map Image 1. Select File Open to bring up the Open dialog. 2. Select All Files (*.*) from the Files of type drop-down. 3. Browse to the demedit\demedit\ directory and select SunValley.jpg. 4. Click Open to exit the Open dialog and import the image. 5. Click Yes if asked to generate image pyramids. The Graphics Window should appear similar to Figure 2. Figure 2 With topo map background Page 4 of 20 Aquaveo 2016

5 3.3 Run TOPAZ 1. Switch to the Drainage module. 2. Select DEM Compute Flow Direction/Accumulation to bring up the Flow Direction/Accumulation Run Options dialog. 3. Click OK to close the Flow Direction/Accumulation Run Options dialog and open the Units dialog. 4. Click OK to close the Units dialog and open the Model Wrapper dialog. 5. Once TOPAZ finishes running, turn on Read solution on exit and click Close to exit the Model Wrapper dialog. 6. Right-click on (Converted) in the Project Explorer and select Display Options to bring up the Display Options dialog. 7. Select DEM Data from the list on the left. 8. On the DEM tab, enter 0.04 as the Minimum Accumulation For Display. 9. Click OK to close the Display Options dialog. 3.4 Basin Delineation 1. Zoom in to the area near the bottom of the project as indicated in Figure 3. Figure 3 Zoom Area 2. Switch to the Drainage module. 3. Using the Create Outlet Point tool, click anywhere on the DEM to create an outlet. 4. Click OK if a message appears stating that the outlet is not located in a flow accumulation cell. 5. In the Properties window on the right side of the WMS display, enter as the Feature Point X and as the Feature Point Y. This moves the outlet location to the new coordinates near the lower right of the area selected in step 1. Page 5 of 20 Aquaveo 2016

6 6. Select DEM Delineate Basins Wizard to bring up the Stream Feature Arc Options dialog. 7. Click OK to close the Stream Feature Arc Options dialog and bring up the Units dialog. This runs the WMS menu commands DEM Stream Arcs, Define Basins, Basins Polygons, and Compute Basin Data. 8. Click OK to close the Units dialog. 9. Click Display Options to bring up the Display Options dialog. 10. Select DEM Data from the list on the left. 11. On the DEM tab, turn off Fill Basin Boundary Only. 12. Select Map Data from the list on the left. 13. On the Map tab, turn on Color Fill Polygons and click Drainage Basin Display Options to bring up the Drainage Basin Display Options dialog. 14. Click the button under Pattern on the left, select Lime from the list of colors, and click OK to close the Drainage Basin Display Options dialog. 15. Select Drainage Data from the list on the left. 16. On the Drainage Data tab, turn on Basin Names, Show Units, Basin Areas, Basin Slopes, and Max Flow Distance. 17. Click OK to close the Display Options dialog. The DEM cells assigned to the delineated drainage basin are now color-filled and should appear similar to Figure 4. Figure 4 Initial delineation results The results do not quite look like what might be expected in an urban area. Even though the drainage basin was delineated using ~10 m elevation data, there are still many Page 6 of 20 Aquaveo 2016

7 features of the urban terrain that are not well represented in the DEM data. One example is the railroad running diagonally across the lower portion of Figure 4 along which the outlet point is located. 3.5 Display Flow Directions The DEM flow directions will show water flowing right across the railroad tracks instead of collecting along the tracks. 1. Click Display Options to bring up the Display Options dialog. 2. Select DEM Data from the list on the left. 3. On the DEM tab, enter 5 as the Point Display Step. 4. Turn on Flow Direction and Points. 5. Click OK to close the Display Options dialog. Notice that flow direction arrows for DEM points are visible. Because the display of flow directions is adaptive, not every DEM point has a flow direction arrow visible. More flow directions are displayed when zooming in and fewer flow directions are visible when zooming out. 6. Zoom in along the railroad tracks until the DEM flow directions for each DEM point are visible. Notice that flow goes right over the railroad tracks. 7. Select Display Display Options to bring up the Display Options dialog. 8. Select DEM Data from the list on the left. 9. On the DEM tab, turn off Flow Direction and Points. 10. Click OK to close the Display Options dialog. 11. Right-click on Drainage in the Project Explorer and select Zoom to Layer. 3.6 Add Stream Arcs Along Railroad In WMS a stream arc can be used to conceptually model runoff collecting along the railroad tracks. 1. Zoom in to the outlet point for the delineated drainage basin. 2. Switch to the Map module. 3. Select the Create Feature Arc tool. 4. Select Feature Objects Attributes to bring up the Feature Arc Type dialog. 5. In the Type section, select Stream and click OK to close the Feature Arc Type dialog. 6. Using Figure 5 as a guide, begin a new stream arc attached to the existing stream arc by clicking on the vertex just upstream of the outlet point. Click far enough away from the outlet point that WMS does not snap to the outlet point. Page 7 of 20 Aquaveo 2016

8 Figure 5 Start point for the railroad stream arc 7. Using Figure 6 as a guide, create the arc along the railroad, double-clicking to end the arc at the location shown by the blue arrow (the orange arrow indicates where the arc started, just to the right of the outlet point). Use the scroll wheel button on the mouse to zoom and pan while creating the arc. Figure 6 Start (orange) and end (blue) points of the railroad stream 3.7 Basin Delineation with the New Stream When the basin is defined, WMS will change flow directions for DEM cells under the stream arc so that they are aligned with the stream arc. The basin definition will then include all area which has flow paths intercepted by the stream arc. The DEM Stream Arcs and Delineate Basins Wizard menu commands for delineating drainage basins should not generally be used once the automated delineation results are manually manipulated in this case, by adding a stream arc to collect runoff along the railroad tracks. This is because WMS will delete all existing feature data except for outlet points when these tasks are performed, removing the stream arcs added for manual manipulation as well. Instead, use the Define Basins and Basins Polygons commands to update the delineation. 1. Switch to the Drainage module. 2. Select DEM Define Basins. Notice that the basin area has expanded significantly. 3. Select DEM Basins Polygons. Page 8 of 20 Aquaveo 2016

9 Notice that the polygon boundary has shifted to encompass the expanded area of the drainage basin (Figure 7). 4. Select DEM Compute Basin Data to bring up the Units dialog. 5. Click OK to close the Units dialog. 6. Right-click on Drainage in the Project Explorer and select Zoom to Layer. The drainage basin data has been recalculated (Figure 7). Figure 7 New drainage basin area with basin data 7. Right-click on (Converted) in the Project Explorer and select Display Options to bring up the Display Options dialog. 8. Select DEM Data from the list on the left. 9. On the DEM tab, turn on Flow Direction and Points and turn off Stream, Flow Accumulation, and Color Fill Drainage Basins. 10. Click OK to close the Display Options dialog. 11. Zoom in to the stream arc along the railroad track until flow directions for each DEM point are visible. Notice that the flow directions are now aligned with the stream arc so that flow no longer crosses the railroad tracks. 12. Right-click on (Converted) and select Display Options to bring up the Display Options dialog. 13. Select DEM Data from the list on the left. Page 9 of 20 Aquaveo 2016

10 14. On the DEM tab, turn off Flow Direction and turn on Stream, Flow Accumulation, Color Fill Drainage Basins, and Fill Basin Boundary Only. 15. Click OK to close the Display Options dialog. 16. Right-click on Drainage in the Project Explorer and select Zoom to Layer. The Graphic Window should appear similar to Figure 8. Figure 8 The drainage basin delineated with the railroad stream 3.8 Save the Project Save the project before continuing with the tutorial. 1. Select File Save As to bring up the Save As dialog. 2. Select Project Files (*.wms) from the Save as type drop-down. 3. Enter advdemdt1.wms as the File name. 4. Click Save to save the project with the new name and close the Save As dialog. 5. Click Yes if asked to save image files in the project directory. It is recommended to Save projects frequently while working on them. Page 10 of 20 Aquaveo 2016

11 4 Depression Points DEM delineation for depressions requires that the low point of the depression be identified as a depression point. 4.1 Depression Attribute 1. Turn off SunValley.jpg in the Project Explorer. 2. Click Display Options to bring up the Display Options dialog. 3. Select Drainage Data from the list on the left. 4. Turn off all options on the Drainage Data tab. 5. Select DEM Data from the list on the left. 6. Turn off Points and Stream and turn on Depression Cells. 7. Enter 1 as the Point Display Step. 8. Select Map Data from the list on the left. 9. On the Map tab, turn off Color Fill Polygons. 10. Click OK to close the Display Options dialog. 11. Zoom in to the area indicated by the blue box in Figure 9. Figure 9 Zoom to depression The contours show that there is a depression here, but the flow accumulations indicate that flow comes in one side and exits the other side of the depression. This occurs because TOPAZ forces flow movement by filling all depressions when processing DEM elevations. 12. Zoom in to the area with the lowest elevation contour line, as indicated by the orange box in Figure 10. Page 11 of 20 Aquaveo 2016

12 Note that contours may not appear exactly as in the image. Figure 10 Zoom to depression pit Within this contour lies the lowest elevation DEM point representing the bottom of the gravel pit. The DEM point with the lowest elevation must be identified so that it can be defined as a depression point in the DEM point attributes. Use the Set Contour Min/Max tool to help indicate the lowest elevation point within this area by changing the contour range minimum and maximum values for viewing in this area. 13. Switch to the Terrain Data module. 14. Using the Set Contour Min/Max tool, click and drag a box around the orange/red contour range as shown in Figure 11. Figure 11 Selection Box for Set Contour Min/Max Tool Page 12 of 20 Aquaveo 2016

13 15. Using the Select DEM Points tool, drag a box around the red contour in the center area to highlight the DEM points in that area. Notice the now-visible DEM point near the center of the red contour area (Figure 12). 16. Select the highlighted point as shown in Figure 12. This DEM point has an elevation of (IJ coordinates of 185,292). This is visible in the Properties section of the WMS screen. Figure 12 Select DEM Point 17. Select DEM Point Attributes to bring up the DEM Point Attributes dialog. 18. In the Attributes section, turn on Depression point and click OK to close the DEM Point Attributes dialog. 19. Using the Set Contour Min/Max tool, right-click anywhere in the Graphics Window and select Clear Min/Max Contour Ranges. 4.2 Run TOPAZ 1. Switch to the Drainage module. 2. Select DEM Compute Flow Direction/Accumulation to bring up the Flow Direction/Accumulation Run Options dialog. 3. Click OK to close the Flow Direction/Accumulation Run Options dialog and bring up the Units dialog. 4. Click OK to close the Units dialog and bring up the Model Wrapper dialog. 5. Once TOPAZ finishes running, turn on Read solution on exit and click Close to exit the Model Wrapper dialog. 6. Zoom to the extents of the depression, if necessary. TOPAZ allows flow from the depression to go to the low point rather than filling the depression once the depression point attribute is assigned. Page 13 of 20 Aquaveo 2016

14 4.3 Create Outlet Point 1. Using the Create Outlet Point tool, create an outlet point in the flow accumulation cell containing the lowest DEM point (as selected in step 4.1, see Figure 13). This is the cell with the DEM point elevation of Figure 13 Location of the outlet point 4.4 Create Stream Arc 1. Switch to the Map module. 2. Select the Create Feature Arc tool. 3. Select Feature Objects Attributes to bring up the Feature Arc Type dialog. 4. In the Type section, select Stream and click OK to close the Feature Arc Type dialog. 5. Create the arc shown in Figure 14, clicking on the outlet point to begin the arc and double-clicking to end it in the lower flow accumulation cell. The arc may not be visible after ending the arc if it is hidden behind the display of DEM flow accumulations. Figure 14 Depression arc Page 14 of 20 Aquaveo 2016

15 4.5 Basin Delineation for the Depression Point 1. Switch to the Drainage module. 2. Select DEM Define Basins. 3. Select DEM Basins Polygons. 4. Select DEM Compute Basin Data to bring up the Units dialog. 5. Click OK to close the Units dialog. Notice that the flow accumulation cells adjusted to the path of the new stream (Figure 15). Figure 15 Flow accumulation cells adjusted to location of stream 4.6 Compute Storage Capacity Curve WMS will use the DEM cells that are part of a selected drainage basin to compute a storage capacity curve given a water surface elevation. 1. Switch to the Hydrologic Modeling module. 2. Using the Select Outlet tool, select the outlet at the depression. 3. Select Calculators Detention Basins to bring up the Detention Basin Hydrograph Routing dialog. 4. Click Define to bring up the Storage Capacity Input dialog. 5. Enter in the field below Use DEM. 6. Click OK to close the Storage Capacity Input dialog and bring up the Detention Basin Analysis dialog. This dialog lists elevation values from the base elevation up to 803 ft of elevation. Along with the elevation values, the computed storage values should also be listed. 7. Click OK to close the Detention Basin Analysis dialog. The curve displayed in the Detention Basin Hydrograph Routing window is the computed storage-elevation curve for the depression pit (Figure 16). 8. Click OK in the Detention Basin Hydrograph Routing dialog. Page 15 of 20 Aquaveo 2016

16 Figure 16 Storage Discharge Curve 5 Time of Concentration Arcs Once DEM cells are assigned to drainage basins, WMS can use the DEM flow directions to automatically create an arc in each basin that represents the longest flow path. This is especially useful for developing times of concentration. 1. Frame the project. 2. Switch to the Drainage module. 3. Select DEM Compute Basin Data to bring up the Units dialog. 4. Click Drain Data Compute Opts... to bring up the Drainage Data Computation Options dialog. 5. Below the list, turn on Create Tc Coverage and click OK to close the Drainage Data Computation Options dialog. 6. Click OK to close the Units dialog. 7. Turn off (Converted) in the Project Explorer. 8. Select the new Time Computation coverage in the Project Explorer to make it active. The Tc arcs generated for each one of the drainage basins should be visible. 6 Polygon Basin IDs to DEM In some situations it is more effective to delineate drainage basins by hand or to import basin boundaries from a GIS or CAD file. 1. Select Drainage in the Project Explorer to make it active. 2. Right-click on GIS Data in the Project Explorer and select Add Shapefile Data to bring up the Select shapefile dialog. Page 16 of 20 Aquaveo 2016

17 3. Select basin_ poly.shp and click Open to import the shapefile and exit the Select shapefile dialog. 4. Turn on (Converted) in the Project Explorer. 5. Zoom in to the area indicated by the blue box in Figure 17. Figure 17 Zoom to Basin Boundary This shapefile contains a more accurate representation of the drainage basin boundaries that exist in this urban area. Notice that the delineation does not exactly match the actual basin boundaries shown in the shapefile (Figure 18). The data from the shapefile can be used to manually update the basin boundaries. Figure 18 Discrepancy in basin boundaries 6. Switch to the Map module. Page 17 of 20 Aquaveo 2016

18 7. Select the Create Feature Arc tool. 8. Select Feature Objects Attributes to bring up the Feature Arc Type dialog. 9. In the Type section, select Generic and click OK to close the Feature Arc Type dialog. 10. Begin an arc by clicking on the vertex shown in Figure 19 (WMS will automatically snap to the existing arc). Figure 19 Start the boundary arc here 11. Digitize an arc along the actual boundary arc, ending the arc by double-clicking when the actual boundary arc intersects the delineated boundary arc again ( Figure 20). Figure 20 End the boundary arc here 12. Turn off GIS Data in the Project Explorer. 13. Using the Select Feature Arc tool, select and delete the arc segment representing the original delineated boundary. 14. Right-click on Drainage and select Zoom to Layer. 15. Right-click on Drainage and select Build Polygon. Page 18 of 20 Aquaveo 2016

19 16. Click OK to use all arcs. 17. Right-click on (Converted) and select Display Options to bring up the Display Options dialog. 18. Select DEM Data from the list on the left. 19. On the DEM tab, turn off Fill Basin Boundary Only and click OK to close the Display Options dialog. Notice that the drainage basins assigned to DEM cells no longer match up with the new drainage basin boundary polygon that was created. This must be corrected in order to properly compute geometric properties of the drainage basin based on the DEM data by using the Compute Basin Data command. 20. Switch to the Drainage module. 21. Select DEM Polygon Basin IDs DEM. 22. Select DEM Compute Basin Data to bring up the Units dialog. 23. Click Drain Data Compute Opts to bring up the Drainage Data Computation Options dialog. 24. Below the list, turn off Create TC coverage and click OK to close the Drain Data Computation Options window. 25. Click OK to close the Units window and compute the basin data. 26. Click OK if notice(s) appear regarding basin edges being encountered. In this case, the messages do not indicate an actual problem because the drainage basin boundary was manually manipulated. 7 Smoothing Boundaries 1. Select Drainage to make it active. 2. Zoom in to any section of the basin boundary. Notice that the boundary arcs are not smooth because they are formed by tracing the square DEM cells. WMS allows redistribution of vertices to smooth these boundaries for reporting and presentation purposes. 3. Select the Select Feature Arc tool. 4. Select Edit Select All. 5. Select Feature Objects Redistribute to bring up the Redistribute Vertices dialog. 6. In the Arc Redistribution section, enter 30.0 as the Average Spacing. 7. Click OK to close the Redistribute Vertices dialog. Notice that the basin boundaries are now much smoother (Figure 21). Page 19 of 20 Aquaveo 2016

20 Figure 21 The basin boundaries are smoother 8 Conclusion This concludes the tutorial. A few of the many advanced basin delineation features were demonstrated that set WMS apart from other GIS-based automated delineation techniques. The tools can be used for many different scenarios where the automated delineation does not yield the expected results. Key topics discussed and demonstrated include: Using stream arcs to manipulate basin delineation Manipulating depressions Developing time of concentration according to the longest flow path Mapping polygons representing drainage basins to the DEMs Smoothing results for reporting and presentations Page 20 of 20 Aquaveo 2016